(1) Field of the Invention
The present invention relates to a mobile communicating system which can provide map information deduced from position information of a mobile terminal, and the mobile terminal, an information center and a storage medium used in the mobile communicating system.
(2) Description of the Related Art
A car navigation system has been well known as a mobile communicating system providing map information to a mobile object deduced from position information of the mobile object. The car navigation system utilizes, in general, GPS (Global Positioning System) as well known, in which current position information (coordinates; a latitude and a longitude) of its own (a motor vehicle, in this case) is detected and map information corresponding to the position information is taken out from a map database equipped in the motor vehicle, whereby the corresponding map information may be displayed on a display along with the current position.
In such the general car navigation system, it is necessary to equip a map database (which is generally provided by a CD-ROM or the like) in each of the motor vehicle utilizing a service and manage it on the user side. For this, the general car navigation system has a drawback such that if an area including the current position changes, the user needs to change the map database (the CD-ROM). This is very inconvenient to the user.
Japanese Patent Laid-Open Publication No. HEI 1-142899 discloses a navigation system in which a map database is provided in a mobile radio base station (hereinafter, simply called "a radio base station), a mobile object (a motor vehicle) transmits the current position of its own detected using GPS or the like to the radio base station, map information corresponding to the position information is retrieved on the radio base station side, and the obtained position information is transmitted to the mobile object that is a source of the transmitted position information.
According to the above car navigation system, the user does not need to manage the map database. Moreover, if the current position of its own (the mobile object) deviates from the map displayed on a display, for example, the mobile object can automatically obtain map information corresponding to the current position information of its own from the radio base station so as to always display a map corresponding to the current position of its own on the display.
All the above car navigation systems have been developed for a high-speed mobile object such as a motor vehicle or the like. There has been also proposed a system for a mobile terminal such as PDA or the like.
For instance, a technique disclosed in Japanese Patent Laid-Open Publication No. HEI 5-37462 can provide map information to a mobile terminal (an electronic pocketbook or the like) following European CT-2 (Second generation Cordless Telephone) standard (corresponding to PHS: Personal Handy-phone System in Japan). In concrete, in this system, when a mobile terminal accesses to a radio base station, map information of an area corresponding to identification information of the radio base station is provided from the radio base station or a service center (an information center) accommodating the radio base station to the mobile terminal.
Each of the above general systems has, however, a drawback that although it is possible to obtain map information indicating the current position of the user (a motor vehicle, a mobile terminal or the like), it is impossible to obtain detailed information relating to the position information such as stores or facilities on the map (telephone number, business hours and the like of facilities on the map) or a service (a service program: a program or the like showing a route to a destination on the map).
The user of the system can obtain map information from the radio base station or the service center, but cannot provide information or a service program relating to position information to the radio base station or the service center to arbitrarily add or update information in the map database. It is therefore very difficult for the radio base station or the service center to always prepare the latest information meeting needs of the users and provide it to the users.
Meanwhile, in such the mobile communicating system which can provide map information from position information of a radio mobile terminal, corresponding map information is retrieved in the map database on the basis of identification information of the radio base station (or a fixed terminal such as a public telephone) as above. For this, database in which information of an actual position (an installation position) of the radio base station or the fixed terminal is corresponded is very important.
The public radio mobile terminal can generally know identification information of a radio base station (or a fixed terminal) to which own terminal is connected, but only the communication company knows actual position information of the radio base station (or the fixed terminal) deduced from the identification information. Accordingly, it is very difficult to independently configure a database in which actual position information of a radio base station or a fixed terminal is corresponded, as above.
Further, in the system handling information having a large data quantity such as map (or image) data as above, a time required from when the user demands information to when the information is transferred from the service center is extremely long, which causes noticeable degradation in operability for the user. The system using a radio line or a public network such as a general telephone line has a disadvantage such that while the user is referring to information on the mobile terminal, no data flows in the communication line although it occupies the line so that a cost of communication becomes extremely expensive.